Ubiquitin - mediated proteolysis of misfolded cytosolic proteins
Final Report Abstract
One central and important function of the ubiquitin/proteasome system (UPS) is the degradation of abnormal or misfolded proteins. In this project, we have analyzed the mechanisms that lead to chaperone-assisted and ubiquitindependent degradation of such proteins. We found, consistent with parallel studies by others, that Hsp70 and Hsp90 and its co-chaperones are required in this process. In the second funding period of this project we investigated which ubiquitin ligases are involved in proteolytic targeting of misfolded cytosolic model substrates in the yeast Saccharomyces cerevisiae. We found that multiple ligases including Ubr1, Hex3/Slx8 and Uls1 contribute to different extents in a complex manner to the degradation of different model substrates. The main focus of our work in this period was on the characterization of the role of Hsp90 chaperones in the proteolytic targeting of proteins. Contrary to reports by others, we found that mutations affecting Hsp90 function in yeast lead to a stabilization not only of misfolded proteins but also to other ubiquitindependent proteasome substrates, which are targeted by specific targeting signals. Our data show that Hsp90 serves a more general function in proteolytic targeting. We found that hsp90 mutants accumulate aggregates of ubiquitylated proteins indicating that Hsp90 chaperones function in the UPS by keeping poly-ubiquitylated substrates in a soluble state suitable for the degradation by the proteasome.
Publications
- "Funktionen molekularer Chaperone in der Qualitätskontrolle zytosolischer Proteine". Dissertation, Universität zu Köln, 2005
Marcel Fröhlich
- (2005). Heat-inducible degron and the making of conditional mutants. Methods Enzymol. 399, 799-822
Dohmen, R.J. and Varshavsky, A.
- "In vivo and in vitro studies on proteasome assembly in Saccharomyces cerevisiae: Possible new roles for Hsp90, ATP, and the 19S regulator". Dissertation, Universität zu Köln, 2006
Christoph Glanemann
- (2006). Ump1 extends yeast lifespan and enhances viability during oxidative stress: Central role for the proteasome? Free Radic Biol Med. 40, 120-126
Chen, Q., Thorpe, J., Dohmen, R.J., Li, F. Keller, J.N.
- (2007). Ubiquitin-dependent Proteolytic control of SUMO conjugates. J. Biol. Chem. 282, 34167-34175
Uzunova, K., Göttsche, K., Miteva, M., Weisshaar, S.R., Glanemann, Schnellhardt, M., Niessen, M., C., Scheel, H., Hoffmann, K., Johnson, E.S., Praefcke, G.J.K. and Dohmen, R.J.
- (2009). Catalytic Mechanism and Assembly of the Proteasome. Chem Rev. 109, 1509-1536
Marques, A.J., Palanimurugan, R., Matias, A.C., Ramos, P.C., and Dohmen, R.J.
- The N-terminal unstructured domain of yeast ODC functions as a transplantable and replaceable ubiquitin-independent degron. (2010). J. Mol. Biol.
Gödderz, D., Schäfer, E., Palanamuragan, R. and Dohmen, R.J.
